Conventional solder systems of the general type with which the present invention is concerned, are employed for soldering ribbon cable leads to the terminals of printed circuit boards. The conventional solder system frequently includes a fixture for retaining the printed circuit board to be soldered, and another fixture positions the ribbon cables leads against the terminals of the printed circuit board. A heater element applies heat to the solder material, to cause it to flow and then to bind the cable leads and the board terminals.
However, with the ever increasing miniaturization of semiconductor integrated circuitry, the degree of tolerance for the pitch between the finely-spaced, hairlike cable leads and the mating board terminals has been substantially reduced. In this regard, the fine pitch requirement for modern integrated circuitry, can not generally be satisfied readily and efficiently by conventional solder devices, in that the alignment of the cable leads with the corresponding board terminals has become increasingly difficult, and in some cases impossible, to achieve by the use of conventional fixtures, prior to the soldering operation. As a result, prior known solder devices have not been entirely satisfactory for many modern applications. The decreased level of accuracy has lead to an alarming high percentage of rejected components, due to improper connection of misaligned leads.
While the foregoing alignment problem can be cured to some extent manually, such solution has proven to be time consuming and inefficient. Additionally, the removal and repair of the improperly soldered components have proven to be less than totally satisfactory, in that they are costly, awkward and time consuming. Hence, the most economical conventional solution to the improper alignment and soldering problems to date, has been to generally discard the defective printed circuit boards, cables and components, rather than to attempt to rectify such problems. In fact, where an improperly soldered ribbon cable electrically interconnects a pair of printed circuit boards, both boards and the cable oftentimes must be discarded.
Therefore, there is a need for a solder system and method of using it, for minimizing, if not totally eliminating, the alignment problems associated with the soldering operation. In this manner, such a solder system should provide a more efficient and effective soldering operation than the conventional soldering devices. The solder system should tolerate the finer pitch alignment of the modern integrated circuitry applications, and it should further enable the user to rectify the improper alignment between the cable leads and the board terminals, prior to affixing the leads in place.
Conventional solder systems, have also been designed to connect surface mounted lead components, such as integrated circuit chips, and hybrid circuit chips, to a printed circuit board. The soldering of different components on a circuit board is generally carried by refixturing the solder system for each type of components, or in the alternative, by using a different solder system for each type of component. Such operation has proven to be time consuming, and thus in some instances prohibitively expensive.
Therefore, there is a need for a solder system and method of using it, for connecting surface mounted lead components to printed circuit boards, without refixturing or changing the solder system, as well as for minimizing the alignment problems associated with the soldering operation of cable and component leads to circuit board terminal leads.
Another problem related to the use of the conventional soldering machines, is the difficulty of reflowing the solder in a precise and proper manner. In this regard, a heating element is generally lowered into a parallel position relative to the printed circuit board, for heating and reflowing the solder to cause it to bind the desired components.
However, in many instances, the heater is positioned improperly relative to the components. Thus, the improper positioning of the heater relative to the rigid fixtures retaining the circuit board and the cable, causes an uneven distribution and application of heat to the solder. Thus, the solder material is not completely and properly heated to a sufficiently flowable condition, for either affixing the leads together or disconnecting them.
Therefore, it would be highly desirable to have a solder system and a method of using it, for minimizing the finer pitch problems associated with the alignment operation of the cable and component leads and board terminals. Furthermore, the solder machine should enable various types of surface mounted lead components to be soldered to the circuit boards without refixturing or otherwise modifying the solder machine. The solder machine should enable the effective connection or removal of the cables, as well as surface mounted lead components, to or from the circuit boards.